Robust line voltage sensor-less control of grid-connected MMC converter in PV Applications

Abstract

This paper discusses the voltage sensor-less control of a single-phase grid-connected Modular Multilevel Converter (MMC) in photovoltaic (PV) applications. The design of the control system is crucial to efficiently injecting PV power into the main grid. Therefore, three control targets are designed. Maximum power point tracking (MPPT) through the Incremental Conductance (IC) algorithm, DC link voltage regulation, and finally output active and reactive power controlling throughout the regulation of grid current amplitude and phase shift. To achieve those targets, the value of grid voltage has to be known accurately. The main contribution of this study is the use of a Simplified Super Twisting Algorithm Sliding Mode Observer (SSTA-SMO) for grid voltage estimation. The effectiveness and satisfactory performance of the proposed system are validated through simulations via MATLAB. To verify the effectiveness of the proposed approach. A study was conducted to evaluate the efficacy of the SSTA-SMO proposal in comparison to a traditional sliding-mode observer. The objective was to showcase the superiority of the proposed approach. The results suggest that the suggested observer surpasses other methods in terms of several aspects, including minimal errors in grid voltage observation, high-quality estimation of grid voltage, and accurate tracking of the reference. Furthermore, it exhibits robustness when exposed to different levels of radiation.